1. Field of the Invention
The present invention relates generally to electrophotographic image forming devices and more particularly to correcting non-ideal feeding behavior of a toner cartridge.
2. Description of the Related Art
In electrophotographic image forming devices, one or more replaceable toner cartridges may be used to supply toner to the device for printing onto sheets of media. When a toner cartridge is installed in an image forming device, the toner cartridge supplies toner stored in a reservoir within the toner cartridge through an outlet port on the toner cartridge to a corresponding inlet port in the device. Toner cartridges often include toner agitators, paddles or augers within the reservoir that fluff and mix the toner to prevent it from clumping and that move the toner to the outlet port.
Toner feed mechanisms have non-ideal feeding behavior such as feed rate that varies with the amount of toner remaining in a toner cartridge. This non-ideal feeding behavior may cause overshooting or undershooting of toner concentration in, for example, a dual component system that uses magnetic carrier beads mixed with toner. Out of bounds toner concentration may cause print defects, dusting of toner within the image forming device, etc. Systems that use a toner concentration sensor often have a delay between when toner is added to the mixture and when the toner concentration sensor settles to a new value. This delay makes it difficult to design a toner concentration control algorithm with small overshot and undershoot when the toner feed rate is not predictable. Further, if a toner concentration sensor is not used (for all or part of the time), variations in toner feed will degrade the control performance and may lead to out of bounds toner concentration.